Numbers 4:20

but they shall not go in to see the sanctuary even for a moment, lest they die.

Exodus 19:21

And Jehovah said unto Moses, Go down, charge the people, lest they break through unto Jehovah to gaze, and many of them perish.

1 Samuel 6:19

And he smote of the men of Beth-shemesh, because they had looked into the ark of Jehovah, he smote of the people seventy men, and fifty thousand men; and the people mourned, because Jehovah had smitten the people with a great slaughter.

Leviticus 10:2

And there came forth fire from before Jehovah, and devoured them, and they died before Jehovah.

Numbers 4:15

And when Aaron and his sons have made an end of covering the sanctuary, and all the furniture of the sanctuary, as the camp is set forward; after that, the sons of Kohath shall come to bear it: but they shall not touch the sanctuary, lest they die. These things are the burden of the sons of Kohath in the tent of meeting.

Numbers 4:19

but thus do unto them, that they may live, and not die, when they approach unto the most holy things: Aaron and his sons shall go in, and appoint them every one to his service and to his burden;

Hebrews 10:19-20

Having therefore, brethren, boldness to enter into the holy place by the blood of Jesus,

Revelation 11:19

And there was opened the temple of God that is in heaven; and there was seen in his temple the ark of his covenant; and there followed lightnings, and voices, and thunders, and an earthquake, and great hail.

Treasury of Scripture Knowledge

Summary

But they shall not go in to see when the holy things are covered, lest they die.

Bible References

They shall

Numbers 4:15
And when Aaron and his sons have made an end of covering the sanctuary, and all the furniture of the sanctuary, as the camp is set forward; after that, the sons of Kohath shall come to bear it: but they shall not touch the sanctuary, lest they die. These things are the burden of the sons of Kohath in the tent of meeting.
Exodus 19:21
And Jehovah said unto Moses, Go down, charge the people, lest they break through unto Jehovah to gaze, and many of them perish.
Leviticus 10:2
And there came forth fire from before Jehovah, and devoured them, and they died before Jehovah.
1 Samuel 6:19
And he smote of the men of Beth-shemesh, because they had looked into the ark of Jehovah, he smote of the people seventy men, and fifty thousand men; and the people mourned, because Jehovah had smitten the people with a great slaughter.
Hebrews 10:19
Having therefore, brethren, boldness to enter into the holy place by the blood of Jesus,
Revelation 11:19
And there was opened the temple of God that is in heaven; and there was seen in his temple the ark of his covenant; and there followed lightnings, and voices, and thunders, and an earthquake, and great hail.

American Standard Version Public Domain